Here's the deal. I can sleep anywhere and on anything. Upright, upside down, trees, logs, rocks, etc. Nothing fazes me. When I climb in the alpine I've never brought along a sleeping pad. Why? Cause I generate a crap ton of heat. Used to not be a problem but it seems my heat engine has kicked it into overdrive lately and I'm generating even more heat than usual. Coupled with my switch to a down sleeping bag from synthetic I find myself waking up 2-3" lower than when I started in snow with a completely soaked bag. Kinda crappy and makes for a pissed off Asian.

So I'm looking for something light and compact that can insulate the ground from me.

Well, most people have the opposite problems. For which there is the ever increasing Thermarest sizes. Mine is now the REI branded 3.5" thick. But for you, if you can really sleep anywhere anytime, I'd go for the cheap thin foam pads like the blue one posted above. There are several other styles brands. But to keep your feet dry when sleeping on snow, I'd go for the long length.

One or two closed-cell blue ones from walmart, etc.. is pretty hard to beat, and the price and weight are right. I also can't say anything bad about the Ridge-Rest, very cushy and light - but a bit pricey by comparison.